build.flake: run service after network.online-target, bump version

Relevant issue can be found here:
https://codeberg.org/tlkg/infrastructure/issues/7

Resolves #87

Decided to use a simpler versioning style.

flake.nix

@@ -16,7 +16,7 @@
 
       hu-announcement-bot = pkgs.stdenv.mkDerivation {
         pname = "hu-announcement-bot";
-        version = "3.8.1";
+        version = "3.9";
         src = ./.;
 
         buildInputs = with pkgs; [
@@ -178,7 +178,7 @@
         systemd.services.hu-announcement-bot = {
           enable = true;
           wantedBy = [ "multi-user.target" ];
-          after = [ "network.target" ];
+          after = [ "network-online.target" ];
           startLimitBurst = 3;
           startLimitIntervalSec = 60;